Final answer:
The vague nerve, or cranial nerve X (CN X), provides sensations from the gastrointestinal tract as part of the parasympathetic nervous system.
Step-by-step explanation:
The sensation from the gastrointestinal tract is provided by the vague nerve, which is cranial nerve X (CN X). This nerve is part of the parasympathetic nervous system and plays a vital role in autonomic control of the thoracic and superior abdominal cavities. The vague nerve is involved in a wide range of functions, including the control of digestive processes through the enteric nervous system. It also mediates the motor response in the gag reflex by directly stimulating the contraction of skeletal muscles in the pharynx and larynx, contributing to swallowing and speech functions.